Question: Suppose the area of a circle is ${16\pi}$. What is its diameter?
Answer: ${K = 16\pi}$ ${d = 8}$ First, find the radius: $K = \pi r^2$ , so $r = \sqrt{K / \pi} = \sqrt{{16\pi} / \pi} = {4}$ Now find the diameter: $d = 2r = 2\cdot {4} = {8}$.